The present invention relates most generally prosthetic limbs. More particularly, the invention provides an improved ankle prosthesis that automatically adjusts to and accommodates a variety of heel heights and surface slopes, most preferably with little or no input from a wearer.
It is well known that users of prosthetic legs must constantly deal with several important issues in order to achieve natural and comfortable walking. A first issue occurs when the user encounters a slope of a ground surface being traversed and walked over. A second issue is produced by changes in the effective xe2x80x98heel heightxe2x80x99 of differing shoes worn over prosthetic feet of a prosthetic limb. Until recently, a common approach was to physically change the foot on the prosthesis, or exchange the entire prosthetic leg when the need for differing heel heights arises. Changes in a ground slope had simply to be tolerated as an uncomfortable reality of prosthetic leg use. For completeness, a. discussion of these issues and specific details associated with changes in heel height, and equivalently, a change in a slope being traversed by an amputee, will now be briefly presented.
The inability to change heel heights causes many physical and safety problems. As an example, consider a xe2x80x98below-the-kneexe2x80x99 amputee. As shown in FIG. 1A, if the heel height of a prosthetic foot/limb is increased at A, an upper portion of the prosthetic leg is forced forward, for example at B. This results in a forwardly directed force or pressure being exerted upon the knee of the wearer. Accordingly, the knee would then have to be stabilized by repeated and possibly excessive use of the quadriceps muscle. Such activities and forces will certainly result in skin irritation, and possibly in blisters and or ulceration of tissue in contact areas.
Similarly, if a heel is lowered, as can be seen in FIG. 1B, a rearwardly oriented force is exerted upon the knee, tilting the leg backwards. In this scenario, there is a possibility of that the wearer will hyper-extend the knee, have difficulty in walking over a now stiff toe lever, and may lead to ligament damage. It may be noted that when considering an above-the-knee amputee, an analogous set of scenarios exist and leads to similar discomforts and injuries.
Another aspect of heel height changes is associated with changes in a slope of a ground surface being walked over and traversed. As is known to prosthetists and other skilled individuals, artificial limbs are essentially designed to be used over smooth and horizontal surfaces. They may function adequately when a wearer has to traverse a short, slight incline. However, each time a hill, ramp, or inclined drive or walkway of any significance is encountered, the above noted problems come to into play. Indeed, step inclines are essentially not traversable without resorting to possibly dangerous and embarrassing maneuvers such as walking sideways with the longitudinal length of the foot perpendicular to the direction of motion.
At present, mechanical heel adjusting means and methods have been difficult to set or calibrate, and do not solve the problem regarding an automatic adjusting to heel height changes, or inclining and declining surfaces. Recently, several noteworthy attempts have been made to address the above described problems and associated issues. However, each of these inventions discloses devices that are quite complicated in structure, and while useful for their intended purposes, do not exhibit the features and advantages of the present invention. For example, these devices have been found to be noisy, heavy, and/or of low reliability. Yet other currently available prosthetic limbs require a wearer to press buttons each time a change occurs in a slope being traversed. This can be very inconvenient, especially in hilly and crowded locations, and may prove embarrassing to some users.
Therefore, skilled individuals will understand a need for simplified, improved, and efficient prosthetic ankle architectures. In particular, there is a need for improved automatically and continually adjusting prosthetic ankles that are simple to operate and reliable. A full understanding of the present invention, including an understanding of a number of capabilities, characteristics, and associated novel features, will result from a careful review of the description and figures of several embodiments provided herein. Attention is called to the fact, however, that the drawings and descriptions are illustrative only. Variations and alternate embodiments are contemplated as being part of the invention, limited only by the scope of the appended claims.
In accordance with the present invention, an auto-adjusting prosthetic ankle apparatus includes a novel damping and. control arrangement. In a preferred embodiment, a base portion is structured for accepting and being fixed to a suitable foot blade. An attachment portion is provided for fixing the prosthetic ankle apparatus of the invention to a lower leg portion of a prosthetic limb. The attachment portion is pivotally fixed to the base portion, thereby enabling a pivoting or pivoting motion between the base portion, and items such as a foot blade that may be fixed thereto, with respect to the attachment portion. For example, a pivoting motion may include a range of plus/minus 10 to 30 degrees, and may enable a pivoting to any selected position between a first position and a second position.
The invention further includes a dynamically controllable damping means. The damping means is structured for functional coupling, or linking, of the base portion and the attachment portion. Importantly, the damping means is arranged to selectively allow unencumbered relative motion of the attachment portion or effectively prevent relative motion thereof, by selecting an amount or level of damping applied to any. relative motion between the base portion and the attachment portion to be one of either a first damping level or a second damping level. In addition, the actual damping level will most preferably be changeable in a rapid and virtually noise free fashion and provide a ratio of a second damping level to a first damping level of at least 10.
An electronics module is provided along with a sensing module including a plurality of sensing devices. The sensing devices enable the apparatus of the invention to determine when: (a) a portion of a prosthetic limb fixed to the attachment portion is moved to a pre-selected substantially vertical orientation, and (b) when a prosthetic foot of a user, which is coupled to the base portion, is contacting a ground surface being traversed by the user. As such, the sensing module may be configured with a level indicating device that may be fixed to the attachment portion (to determine when the orientation thereof is at the pre-selected substantially vertical orientation) and a ground surface contacting sensor.
Embodiments of the sensing module are to be structured for determining over what temporal intervals in a walking cycle the damping level is to be set to a first damping level and at what temporal intervals the damping level is to be set to a second damping level. As an astute observer will appreciate, the advantage of selectively and dynamically alternating between a first and second damping level may result in a much more natural gait and walking motion, along with the ability to automatically adjust the prosthetic ankle of the invention to changes in heel height and the slope of a ground surface being traversed. A preferred dynamic controlling of the damping means will result in a first damping level being established for a first interval of a walking cycle of a user, with a second damping level being established for a second interval (of the same walking cycle).
A control and computing means is included for receiving information from the sensing means for determining how and when a selected level of damping applied between the base portion and the attachment portion is to be altered. The control and computing means may be interfaced to a suitably miniaturized user interface, which may include one or more input devices (e.g., switches and pushbuttons) and one or more output devices such as a small display or annunciator elements.
As will be discussed in great detail hereinafter, the most preferred embodiments of the dynamically controllable damping means will include a hydraulic system including one or more hydraulic cylinders providing a plurality of hydraulically coupled internal pressure cylinders. A preferred form of realizing the dynamically controlled damping of pivoting motion between the base portion and the attachments structure simply controls the flow of fluid that is transferred from a first internal pressure chamber to a second internal pressure chamber. In a most preferred embodiment of the hydraulic system of the invention, magnetorheological fluids are employed to selectively, quietly and rapidly vary the damping level between the first level and the second level without the activation of any moving parts.